Thread brake

ABSTRACT

The thread brake has two oppositely disposed braking surfaces at least one of which has an indentation to limit lateral movement of the thread during braking. The indentation can be of uniform groove shape and of a depth less than the thickness of a thread or can have a transition zone formed by a chamfered wall which merges on an obtuse angle into the braking surface.

United States Patent [1 1 UNITED STATES PATENTS 1/1949 Houseman 188/652Pfarrwaller 51 Dec. 30, 1975 [54] THREAD BRAKE 2,608,845 9/1952 Brown66/145 1 Inventor: Erwin Harman, wimwhw, i'lil'ifi 211322fifiill'lgzzijij la /.22

Switzerland [73] Assignee: Sulzer Brothers Limited wintenhur'Switzerland Primary Exammer-l-lenry S. .laudon Attorney, Agent, orFirm-Kenyon & Kenyon Rally [22] Filed: Apr. 2, I974 Carr & Chapin [21]Appl. No.: 457,235

[30] Foreign Applic'ation Priority Data [57] ABSTRACT Apr. 3, 1973Switzerland 4723/73 The thread brake has two oppositely disposed brakingsurfaces at least one of which has an indentation to gg fg lgg limitlateral movement of the thread during braking. The indentation can be ofuniform groove shape and [58] Field of Search 139/122 R, 122 H, 194;

H25 226/195 [88/651 65 2 65 3 of a depth less than the thickness ofathread or can 65 A have a transition zone formed by a chamfered wallwhich merges on an obtuse angle into the braking sur- [56] ReferencesCited face 10 Claims, 6 Drawing Figures US. Patent Dec. 30, 1975 Sheet 10f 2 3,929,169

US. Patent Dec. 30, 1975 Sheet 2 of2 3,929,169

THREAD BRAKE This invention relates to a thread brake and particularlyto a thread brake for use in braking weft threads in a loom.

Heretofore, various types of thread brakes have been known for brakingthreads during travel, for example in textile machines such as looms.Generally, the thread brakes have been constructed with two brakemembers having overlapping braking surfaces which are adapted todecelerate a thread that runs between the surfaces. However, in threadbrakes of this kind it is possible for the thread which is gripped bythe brake members, particularly if the thread passes through the brakemembers intermittently to deviate laterally during braking. As a result,in many instances, the threads have become positioned outside thebraking position and become loose. This may be caused by the unavoidableminor deviations of parallelity in the braking surfaces, particularly inconjunction with vibrations of the brake members of thread brakes whichare disposed in an operating machine.

A thread which emerges laterally from the brake gap between two brakingsurfaces is frequently unable to re-enter between the brake members.Thus, the thread cannot be braked in a subsequent thread motion andcauses an operational breakdown. Any such misalignment of a stationarythread is particularly detrimental in machines, for example looms, whoseelements operate reliably only if the thread remains taut. For example,the transfer of thread between a thread supply means and a shuttle maybe detrimentally affected or rendered impossible in gripper-type shuttleloom.

Accordingly, it is an object of the invention to ensure reliablegripping of a thread in a thread brake. It is another object of theinvention to impose as small as possible a stress on a thread which isperiodically braked to a stop during travel.

It is another object of the invention to prevent a lateral deviation ofa thread out of a thread brake during operation of the brake.

Briefly, the invention provides a thread brake which has a pair of brakemembers, each of which has a braking surface, with an indentation in atleast one of the braking surfaces. The indentation is disposed laterallyof the path which a thread takes in passing longitudinally between thebraking surfaces and is sized to receive the thread. The thread sectionthat is disposed between the braking surfaces is therefore able totravel laterally only within a precisely defined range before beingcaught in the indentation.

In one embodiment particularly intended for the deceleration of tautthreads with an accurately defined thread run, the indentation has theform of a groove that extends substantially parallel to the path of thethread.

In order to ensure a constant deceleration of the thread, i.e. even fora thread that has already been laterally displaced, it is appropriate ifthe depth of the indentation is less than the thickness of the threadthat has to be decelerated.

In a further embodiment, the transition zone between the braking surfaceand the indentation is constructed so as to avoid additional stressingof the thread, particularly during each recommencement of the threadmotion after a stoppage. For example, the wall of the indentationnearest to the braking position is cham- 2 fered or otherwise formed tomerge on an obtuse angle into the braking surface.

These and other objects and advantages of the invention will become moreapparent from the following detailed description and appended claimstaken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically illustrates a thread brake of the invention inan open position, shown partially as a longitudinal section;

FIG. 2 illustrates a horizontal sectional view taken along line II-II ofFIG. 1;

FIG. 3 illustrates a view of the thread brake according to FIG. 1 in abraking position;

FIG. 4 illustrates a cross-sectional view taken along line IV-IV of FIG.2;

FIG. 5 illustrates a modified thread brake according to the invention;and

FIG. 6 illustrates a further modified yarn brake according to theinvention.

Referring to FIG. 1, the thread brake has a flexible brake member 1 anda rigid brake member 2 which cooperates with each other to brake athread 19 passing longitudinally therebetween in a predetermined path.The brake member 1 comprises a flexible strip 3, for example a steelband, both ends of which are secured to holders 4, 5 each of which isprovided with an eyelet 4a, 5a respectively, for passage of the thread19. The holder 4 is mounted on a support member 6 of a loom (not shown)and the holder 5 is disposed on an arm 8 which is pivotable in thedirection indicated by an arrow 7 and is situated on a shaft 9 that isassociated with the drive (not shown) of the loom.

The brake member 2 comprises a plate which is disposed on a shaft 11 andone side of the brake member 2 forms a cylindrically curved smoothbraking surface 12. This surface 12 overlaps a corresponding smoothbraking surface 10 on the strip 3 as indicated in FIGS. 2 and 4. Theshaft 11 is axially slidably guided in the directions indicated by anarrow 14 in a bearing 13 that is disposed on the loom (not shown). Theshaft 11 is provided with a collar 15 on which a compression spring 16acts that bears on the bearing 13. The compression spring 16 causes theend of the shaft 11 to be thrust against a cam 17 which is mounted on ashaft 18 that is associated with the loom drive (not shown).

The thread 19 is supplied from a supply reel (not shown) through theeyelet 4a to pass between the brake members 1, 2 and exit through theeyelet 5a. For example, the thread 19 is a weft thread of the loom whichis guided downstream of the eyelet 5a, as indicated by the arrow 20, toa weft picking device (not shown) and is intermittently transferred bythe picking device into a shed. The thread is kept tensioned betweenevery two weft picks by means of a thread tensioner (not shown) that isdisposed between the supply reel (not shown) and the thread brakemembers 1, 2.

Referring to FIGS. 2 and 4, in order to limit lateral movement of thethread 19, the braking smooth surface 11 of the rigid brake member 2 isprovided with two indentations 21, 21a which define the brake positionand extend in laterally spaced parallel planes to the direct thread pathdefined by the eyelets 4a and 5a. These indentations 21, 21a areprovided on both sides of the smooth portion of the brake surface 11which defines the thread path and have a groove-shaped cross-section ofa depth h (FIG. 4) which is less than the thickness of the thread 19which is to be decelerated. Each indentation 21, 21a has a wall 22nearest to the thread path which is chamfered and merges on an obtuseangle into the braking surface 12.

The thread brake (1, 2) is adjusted so that when the brake is in theopen position (FIG. I), the brake member 2 is maintained at a distancefrom the taut strip 3 that will permit unobstructed passage of thethread 19, for example while the thread is being picked as a weft. Inthe end phase of the weft picking operation, the brake member 2 isguided into the position 2' (FIG. 3) through a half rotation of the cam17 which is controlled by the loom drive. This causes the strip 3 to beflexed into the position 3' by a simultaneous pivoting motion of the arm8 so that the strip 3 together with the thread 19 hugs the brake member2. The thread 19 is then decelerated between the smooth portions of thetwo brake surfaces 10, 12 by friction and is finally braked to a stop.After a predefined period of time, the brake member 2 is guided backinto the position shown in FIG. I by a further half rotation of the cam17 so that the thread 19 is released, for example for a succeeding weftpicking motion.

For the reasons mentioned initially, the part of the stationary thread19 which is gripped in the closed thread brake has the tendency ofdeviating laterally from the brake position which is disposed in thedirect thread path. Accordingly, the thread portion disposed between theeyelets 4a, a is curvilinearly deflected into the position 19' (FIG. 2)particularly in the course of prolonged braking, for example in multipleweft looms with an alternating weft picking motion, and finally passesvia a chamfered wall 22 into the zone of the indentation 21 or 21a inwhich the thread 19 is caught.

Owing to the depth h of the indentation 21, 21a being less than thethread thickness and because of the contact force of the brake member 2or the elasticity of the strip 3, the thread section is retained in theindentation 21, 21a and is released only when the thread brake isreleased. The chamfered walls 22 of the indentations 21, 21a facilitatethe reception and release of the thread section so that, in practice,the thread is not subjected to any additional stresses.

Referring to FIG. 5, wherein like reference characters indicate likeparts as above, the brake member can also be made with a flexible brakemember 1 which has each end mounted on a stationary support member 25 tocooperate with a brake member 26 which is mounted on a holder 28 that ispivotable in the directions indicated by an arrow 27. The holder 28 isdisposed on a shaft 29 that is controlled by the loom drive (not shown).The brake member 26 has a smooth substantially plane braking surfacewhich is provided with two parallel indentations 32, 32a that extendover the entire length of the member 26. These indentations 32, 32a areconstructed as half round grooves, the depth h of which is less than thethickness of the thread I9.

Pivoting motions derived from the loom drive cause the brake member 26to be moved against the thread 19 into the brake position illustrated inFIG. 5 or to be moved out of this position into a release position inwhich the thread 19 is released. Flexing of the strip3 under the actionof the brake member 26 during the braking operation is only slight ordoes not take place at all. Accordingly, only slight pivoting motionneed be imparted to the holder 28 via the shaft 29 and braking becomesstronger. The flattened piece of the thread which moves laterally intothe position 19' moves into the indentation 32 or 32a and is retaineduntil the thread brake is lifted.

As shown, it is possible to dispense with a special construction of thetransition zone between the brake surface 31 and the associated walls ofthe indentations 32, 32a in favor of a simpler construction ormanufacture of the brake member 26.

Referring to FIG. 6, wherein like reference characters indicate likeparts as above, the thread brake may also be constructed of two plateshaped brake members 35, 36 with smooth plane braking surfaces 37, 38,respectively. The brake member 35 is provided with a singlegroove-shaped indentation 39 for accommodating the thread portion thatis displaced laterally into the position 19'. In addition, a guide strip40 is provided on an opposite side of the thread path to limit anylateral motion of the thread 19 in the other direction. As shown, theguide strip 40 is in laterally spaced relation to the edge of the brakemember 35 and is mounted adjacent to the brake member 36. The brakemember 39 is disposed on a resilient base 41 on a support member 42 ofthe machine. The brake member 35 is mounted on a shaft 11 which ismovably supported in the directions indicated by the arrow 14 in themanner already described hereinbefore and is guided via the cam 17 intothe brake position illustrated in FIG. 6 or into a released position inwhich the thread 19 is released.

Other embodiments of the invention are also possible. For example, theindentation for accommodating the thread may be provided in the brakingsurface of a flexible brake member. The flexible brake member may alsobe constructed of a material other than steel, for example light alloy,titanium or a plastics material and may also be provided with a coveringof wear resistant material. Furthermore, each of the two cooperatingbrake members may have an indentation.

The invention can also be applied to thread brakes with othercooperating brake members, for example brake jaws.

Instead of providing a groove-shaped indentation, one of the brakingsurfaces may also have an indentation of a different shape, for examplea bore suitable for accommodating the thread and also disposed in alaterally spaced parallel plane to the normal thread path to retain athread within the limits of the brake members.

The thread brake of the invention can be employed for other textilemachines in addition to looms and is particularly advantageous formachines with thread brakes for threads which run intermittently.

What is claimed is:

I. A thread brake comprising a pair of brake members for movementagainst each other for braking a thread passing longitudinallytherebetween in a predetermined path, each brake member having a smoothbraking surface opposite each other to define said path therebetween,and an indentation in at least one of said braking surfaces disposed ina laterally spaced parallel plane to said path, said indentation beingsized to receive a braked thread therein to retain the thread within thelimits of said brake members.

2. A thread brake as set forth in claim 1 wherein said indentation isgroove-shaped in cross-section and extends longitudinally of said onebraking surface parallel to said path.

3. A thread brake as set forth in claim 2 wherein said indentation is ofa depth less than the thickness of the braked thread.

4. A thread brake comprising a pair of brake members, each said memberhaving a smooth braking surface disposed opposite a smooth brakingsurface on the other said member to define a thread path therebetween;and an indentation in at least one of said braking surfaces forreceiving a braked thread to limit lateral movement of the threadrelative to said braking surfaces during closing of said surfacesrelative to each other said indentation being disposed parallel and inlaterally spaced relation to said path.

5. A thread brake as set forth in claim 4 which further comprises aguide strip on one side of a thread path passing between said brakemembers opposite said indentation, said strip being disposed inlaterally spaced relation to one brake member and mounted adjacent theother brake member to limit lateral movement of the thread relative tosaid braking surfaces.

6. A thread brake as set forth in claim 4 wherein said indentation is ofsemi-circular cross-sectional shape.

7. A thread brake as set forth in claim 4 wherein one of said brakemembers is a flexible strip.

8. A thread brake comprising a pair of brake members for braking athread passing longitudinally therebetween in a predetermined path, eachbrake member having a braking surface opposite each other, and anindentation in at least one of said braking surfaces disposed laterallyof said path, said indentation being sized to receive a braked threadtherein and including a wall on a side nearest a braking positionmerging into said one braking surface at an obtuse angle.

9. A thread brake comprising a pair of brake members, each said memberhaving a braking surface disposed opposite a braking surface on theother said member; and two indentations in at least one of said brakingsurfaces spaced on either side of a thread path passing between saidbrake members for receiving a braked thread to limit lateral movement ofthe thread relative to said braking surfaces during closing of saidsurfaces relative to each other.

10. A thread brake comprising a pair of brake members, each said memberhaving a braking surface disposed opposite a braking surface on theother said member; and an indentation in at least one of said brakingsurfaces for receiving a braked thread to limit lateral movement of thethread relative to said braking surfaces during closing of said surfacesrelative to each other, said indentation being of groove-shapedcrosssection and including a chamfered wall nearest a thread pathpassing between said brake members, said wall merging on an obtuse angleinto said one braking surface.

It l=

1. A thread brake comprising a pair of brake members for movementagainst each other for braking a thread passing longitudinallytherebetween in a predetermined path, each brake member having a smoothbraking surface opposite each other to define said path therebetween,and an indentation in at least one of said braking surfaces disposed ina laterally spaced parallel plane to said path, said indentation beingsized to receive a braked thread therein to retain the thread within thelimits of said brake members.
 2. A thread brake as set forth in claim 1wherein said indentation is groove-shaped in cross-section and extendslongitudinally of said one braking surface parallel to said path.
 3. Athread brake as set forth in claim 2 wherein said indentation is of adepth less than the thickness of the braked thread.
 4. A thread brakecomprising a pair of brake members, each said member having a smoothbraking surface disposed opposite a smooth braking surface on the othersaid member to define a thread path therebetween; and an indentation inat least one of said braking surfaces for receiving a braked thread tolimit lateral movement of the thread relative to said braking surfacesduring closing of said surfaces relative to each other said indentationbeing disposed parallel and in laterally spaced relation to said path.5. A thread brake as set forth in claim 4 which further comprises aguide strip on one side of a thread path passing between said brakemembers opposite said indentation, said strip being disposed inlaterally spaced relation to one brake member and mounted adjacent theother brake member to limit lateral movement of the thread relative tosaid braking surfaces.
 6. A thread brake as set forth in claim 4 whereinsaid indentation is of semi-circular cross-sectional shape.
 7. A threadbrake as set forth in claim 4 wherein one of said brake members is aflexible strip.
 8. A thread brake comprising a pair of brake members forbraking a thread passing longitudinally therebetween in a predetermInedpath, each brake member having a braking surface opposite each other,and an indentation in at least one of said braking surfaces disposedlaterally of said path, said indentation being sized to receive a brakedthread therein and including a wall on a side nearest a braking positionmerging into said one braking surface at an obtuse angle.
 9. A threadbrake comprising a pair of brake members, each said member having abraking surface disposed opposite a braking surface on the other saidmember; and two indentations in at least one of said braking surfacesspaced on either side of a thread path passing between said brakemembers for receiving a braked thread to limit lateral movement of thethread relative to said braking surfaces during closing of said surfacesrelative to each other.
 10. A thread brake comprising a pair of brakemembers, each said member having a braking surface disposed opposite abraking surface on the other said member; and an indentation in at leastone of said braking surfaces for receiving a braked thread to limitlateral movement of the thread relative to said braking surfaces duringclosing of said surfaces relative to each other, said indentation beingof groove-shaped cross-section and including a chamfered wall nearest athread path passing between said brake members, said wall merging on anobtuse angle into said one braking surface.